Conventionally electromagnetic pumps operate from mains power and the compressors within the electromagnetic pumps operate directly from this single phase mains power which provides the compressor electrical drive input voltage and frequency. Therefore these compressors operate at constant fluid flow, and any fluid flow control depends merely on on/off control or on fluid loading conditions. The necessary fluid flow rates are obtained by the control and design of the fluid routing system.
Such compressors include linear or arcuate motion reciprocating actuators driven by electromagnetic drive means supplied by the mains power voltage and frequency. The electromagnetic drive means drive the actuators into reciprocating mechanical motion which is translated by diaphragms and valves into fluid flow from one or more compressor inputs to one or more compressor outputs.
This approach has a number of problems including the design of the compressor having to vary with the value of mains power voltage and frequency, complicating manufacture and driving up costs. Furthermore, flow control only by air routing compromises the compressors' life, the compressors having to be operated continually at maximum capacity with the consequence of maximum noise and vibration during use.
Furthermore, the performance of the compressors is largely dependent on the mechanical characteristics of its components, for example the diaphragm stiffness, the moving mass, and also the stiffness of the compressed air within the pump.
Any variation either between units of manufacture or within environmental operating conditions or through use will cause additional performance variation.
Thus, those skilled in the art have long recognized the need for a fluid flow control system for an electromagnetic pump that is not dependent on the voltage and frequency of the mains power supply and provides the desired fluid flow with the optimum performance of the pump.